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Morphology
- Gram Positive Cocci
- Non-motile
- Non-spore forming
- Arranged in irregular clusters
Culture
- Grow on most media in aerobic conditions
- Staphylococcus aureus is golden
- Staphylococcus epidermidis is white
- Resistant to drying & heat
Resistance
- To many anti-microbials
- ß-lactamase production
- Plasmid mediated
- Resistant to some Penicillins & Cephalosporins
- Methicillin Resistance
- Independent of ß-lactamase production
- Mechanism unknown
- Function of cell wall structure
- Tolerance
- Inhibition without death
- Due to lack of activation of autolytic enzymes (PBP) in cell wall
Toxins & Enzymes
- Exotoxin
- Alpha-haemolysin
- ß-haemolysin
- Endotoxin C
- Are haemolytic & pyogenic
- Enterotoxin
- Food poisoning
- Protein that clots citrated plasma
- S Aureus produces it » Coagulase Positive
- S Epidermidis doesn’t » Coagulase Negative
- Synonomous with invasive potential
- Other
- Hyalurodinase
- Staphylokinase
- Exfoliative toxin
- “Toxic Shock Syndrome” toxin
Pathogenesis
- Staphylococcus aureus
- Staphylococcus epidermidis
- Found on skin
- Rarely suppurative
- May infect prostheses
Pathology
- Abscess
- Prototype infection
- Furuncle, carbuncle, pimple
- Focal suppuration & necrosis
- Coagulase coagulates fibrin around lesion to produce wall
- Liquefaction of necrosis occurs
Treatment
- Made difficult by
- Resistance to AB
- Hypovascular abscess
- Biofilm with biomaterials
- Drainage of pus important » Key
- Most staphylococci are Penicillin resistant
- Many are Flucloxacillin resistant
- All are sensitive to Vancomycin
